The present invention relates to a pyrolyzer and use thereof, and more particularly, to a micropyrolyzer capable of pyrolysis, heated chemistry, or thermal desorption of small liquid and solid samples for subsequent gas phase chemical analysis.
Pyrolysis is the rapid decomposition or dissociation by thermal energy of materials into smaller chemical fragments. As a sample preparation and introduction technique, pyrolysis can be performed on a wide variety of samples ranging from aerosols and complex polymers to biological samples. By such rapid heating, solids can be decomposed or dissociated, liquids can be vaporized, and species within a liquid can also be decomposed. In practice, programmed temperatures from 300 to 1000° C. are applied to the liquid or solid sample in a short time duration, typically ranging from milliseconds to a few seconds. The gas phase products of the sample pyrolysis are usually introduced or transferred into another device for some type of chemical analysis. These analysis devices can include a gas chromatograph (GC), mass spectrometer (MS), spectrophotometer, or other chemical analysis separator and/or detector. While these analysis devices are being reduced in size for commercial use, currently available commercial pyrolyzers require large power sources that are not compatible with field use. In addition, conventional pyrolyzers use metal wires or foils for heating, which may be incompatible with some sample materials.
There are several types of instrumentation used to perform pyrolysis, including gas chromatographic inlet, infrared, Curie-point, and resistive pyrolyzers. In gas chromatographic inlet pyrolysis, a liquid sample is introduced into the heated inlet of a commercial gas chromatograph and vaporized for subsequent analysis. In the infrared pyrolysis method, pulsed infrared laser radiation rapidly heats the sample, depending upon the irradiance or energy per unit area focused upon the sample during the pulse. In Curie-point pyrolysis, a magnetic metal foil or wire of particular alloy composition is excited by radio frequency energy. The metal heats until the characteristic Curie-point temperature of the alloy is reached, at which point the metal is no longer magnetic and ceases to heat. Resistive pyrolysis is perhaps the simplest of the common pyrolysis methods, requiring only a metal filament (often platinum) and a capacitive power supply capable of sending a large current rapidly through the filament.
Heated chemistry is used to derivatize (chemically react) an analyte to form a new species that has enhanced properties for analysis in a gas chromatograph or other analysis unit. The new species is often more volatile, or may have more desirable properties for subsequent detection (such as adding chlorine for electron capture detection). The derivative chemistry reactions are often performed in separate glassware, followed by injection into the gas chromatograph for vaporization and analysis.
Thermal desorption is a common technique for recovering (for analysis) volatile and semi-volatile chemical species from solid samples. Examples include gasoline components from soils, phthalates from plastic components, and volatile organic compounds (VOCs) from many types of solids. Heating is usually limited to an upper limit of about 350° C. due to the polymeric gaskets used to connect the heating device to the analytical instrument.
Pyrolysis, heated chemistry, and thermal desorption for chemical analysis have applications both in the standard laboratory and in field use. Applications of interest to the government include non-proliferation monitoring, counter-terrorism and first responder efforts, and chemical and biological warfare agent detection. Applications of interest to industry include efficient industrial process control, emissions control, water and air quality monitoring, food and water safety, agricultural quality control, biomedical diagnostics, and law enforcement activities such as drug and forensic analyses. Additional applications include the analysis and/or identification of bacteria, fungi, micro-organisms, and various pathogens and pathogenic activity in both animals and plants for food and water safety, biologically active process monitoring, and industrial hygiene.
Conventional pyrolyzers have several shortcomings for many of these applications. Conventional pyrolyzers can require large power supplies and control units and costly equipment. For example, a commercially available Curie-point pyrolyzer can require tens of Watts of power, occupy over 10,000 cm3 of space, and weigh nearly 20 kg. In particular, due to increased regulations, cost issues, and public concern, there exists a need for field portable analyzers for on-site contamination detection and remediation, process control, emission monitoring, and other applications.
The micropyrolyzer of the present invention enables the development of a truly portable, self-contained (e.g., battery operated) pyrolysis-based analyzer that is not available with conventional analysis devices. The ability of the micropyrolyzer to be integrated with other on-chip components allows reduced operation, manufacture, and replacement costs; increased flexibility; and increased portability. Furthermore, the micropyrolyzer can be constructed from semiconductor materials, thereby enabling analysis of chemical samples that may be reactive with the metal wire or foil heating elements of conventional pyrolyzers. For pyrolysis, the micropyrolyzer allows smaller samples with lower dead volumes to be heated to higher temperatures, reducing sample consumption and power requirements and providing a wider range of available procedures. For heated chemistry, the micropyrolyzer enables derivatization and vaporization of a small sample to be performed in the same device. For thermal desorption from solids, the micropyrolyzer enables a needed portable field unit.